For example, an apparatus having a map display function such as car navigation has a three-dimensional map bird's-eye-view display function to arrange building models such as commercial facilities on a rough three-dimensional terrain model, and display the terrain model, and the building models in a bird's-eye-view manner. The data for realizing the three-dimensional map bird's-eye-view display function is generally the terrain model and/or building models of three-dimensional information that are provided by a map data production company. These pieces of three-dimensional information are made based on data through field positioning. However, the field positioning of the three-dimensional information on the terrain and buildings involves errors, and thus, there is a problem such that when a three-dimensional map based on the three-dimensional information is displayed, the building models rise from the terrain model or the building models sink in the terrain model.
As a countermeasure against this, Patent Document 1 discloses altitude correction processing compatible with an actual terrain including: extracting, from three-dimensional terrain data, altitudes at respective vertex coordinates of a building bottom surface to be subjected to the processing; adding the maximum value out of the extracted altitudes to the height coordinates of the vertices other than the building bottom surface as a reference altitude of the building; and adding the minimum value out of the extracted altitudes to the height coordinates of the vertices of the building bottom surface as a bottom surface altitude of the building to thereby restrain the building models from rising from the terrain model, or restrain the building models from sinking in the terrain model.